1. Field of the Invention
The present invention relates to a technique for removing particles from a processing tank storing a liquid in a substrate processing apparatus for performing a process by dipping substrates including a semiconductor substrate, a glass substrate for a liquid crystal display, a glass substrate for a photomask and the like in the liquid.
2. Description of the Background Art
Conventionally, a dip-type substrate processing apparatus for processing substrates by dipping the substrates in a liquid such as deionized water and liquid chemicals has been known in the manufacturing steps of the substrates. The dip-type substrate processing apparatus includes a processing tank for storing a liquid, and performs a cleaning process and the like on substrates in the processing tank.
In such a substrate processing apparatus, particles generated within the processing tank are removed during a process of substrates or during a time interval between processes (a time interval between processing a group of substrates and processing a next group of substrates). Typically, the substrate processing apparatus filters a liquid overflowing the top of the processing tank and supplies the liquid again through a bottom portion of the processing tank, thereby to reduce the number of particles within the processing tank.
As discussed above, the conventional particle removal method has used only the action of a circulating liquid flow to carry and remove the particles. However, there is a fixed limit to the efficiency of particle removal because the conventional method depends on only the action of the liquid flow. In recent years, it has been a challenge to further shorten the time required to manufacture the substrates, and an acceptable particle level has become increasingly strict. This necessitates a technique capable of removing particles within the processing tank in a shorter time with efficiency.